
I think you need to read the chapter again. Mr. Kim said that he thinks he's overstepping because in the first place, he shouldn't have any connection with Sejin but being his secretary. Are u aware of NDA? Non disclosure agreement? Do you know why Mr Kim is considered as whistle blower? It's because he saw things that was just wrong but he can't speak about it because its his employer who happens to be one of the most influential ppl in the country. Do you understand why he waited 21 years before speaking up? Because it took 21 years for Ido to show up. The one who can drag Haeshin down.
This is why its important to understand the society, life, universe of fcking dimension the story is set on before you make judgement. In this world, Sejin and Mr. Kim were powerless compared to Haeshin. They can't do anything to save each other let alone save themselves.
Mr. Kim is an ordinary salary man for God's sake, what can he do against a powerful corporation who can literally end his life (and/or his wife) in just a snap of a finger?

you need to understand sejin wasn't abused in a typical way, he was emotional abused and neglected while also being brainwashed to 'repay' them. Sejin was fed, clothed and educated. So what can the cop or cps even do? Haeshin didnt break any laws, and even if Mr. Kim helped him run away, did sejin want to run away? I think sejin's reaction to ido's action is proof that he wanted to maintain his semblance of a family because he doesn't want to be a 'orphan' or 'alone'. If Mr. kim stepped out of line he would have been removed and sejin really wouldn't have anyone on his side

I get that you're feeling frustrated at him, and I also think you're valid for feeling that way. But the other comments also raised good points, like, Haeshin is really a big name to go against that Mr. Kim really wouldn't be able to do anything significant for Sejin, until he acted as a whistleblower BECAUSE Ido can protect him.
Even Sejin felt Mr. Kim was just a bystander to everything he went through all these years, that's why he felt betrayed at first. But when Mr. Kim explained a bit about his side, Sejin understood where Mr. Kim was coming from. It wasn't much, yes, but it was what Mr. Kim could do for Sejin then, and now he can do so much more for Sejin now that they're both out of Haeshin.
Im sorry but im not buying the secretary's excuses.
He watched for 20 years a little boy get abused by his adoptive family and did NOTHING, not a single thing to protect him and now he says he thinks of him as a son?!
Conveniently he was ready to save his "son" only after his husband gave him money to betray his current job.